The invention pertains to machine tools wherein a saddle or slide is to be precisely aligned for movement along a set of parallel ways. In one useful application, the invention is used in association with a saddle carrying a spindle and spindle drive which must be moved along a set of ways to machine a workpiece. In order for the machine operation to be accurate, the axis of the spindle must be in strict parallel relation to the ways as a rotary cutter driven by the spindle is brought into engagement with the workpiece.
In a typical arrangement for keeping the axis of a vertical machine tool spindle carried by a saddle in alignment with a set of vertically positioned ways, slots are formed in the saddle to receive the ways in sliding relationship. If the ways are of a type referred to as flat ways, they each have a flat forward surface and orthogonal sides, and the slots have bases and sides which respectively match the flat surface and sides of the ways. Members known as keepers are attached to the saddle and extend behind the ways to prevent transverse movement of the spindle relative to the ways as the saddle moves vertically along the ways. The keepers also prevent the spindle and its associated spindlehead, which project outward from the ways, from rotating downwardly.
In arrangements of the above type, the keepers are generally joined to the saddle by means of bolts or screws which are subjected to, and must take up, both horizontal and vertical loading of the saddle. As a result, keepers are frequently broken loose from the saddle. Also in such arrangements, wear tends to occur between the sides of the slots and the sides of the ways as the saddle moves vertically. It is therefore necessary to place adjustable gibs or like devices between the saddle and the ways to take up way-induced clearance.